Airline companies ordering aircraft often specify a number of design options to the manufacturer, including passenger seating layout. The manufacturing and inventory costs incurred in providing different seating arrangements and spacing between seats can be significant, and will be particularly important in the next generation of aircraft that will offer new personal entertainment and service facilities to each passenger. Designers are planning to install an entertainment system and passenger service system in the back of each seat on such aircraft. Consequently, each seating arrangement that an airline company might specify would typically require different length power lead harnesses to supply power to the seats. The cost and weight penalty associated with providing power for each seat using conventional techniques would likely be unacceptable to most passenger carriers.
An alternative to wiring each seat to a power source is disclosed in commonly assigned U.S. Pat. No. 4,428,078 (C. Kuo). This patent discloses what is referred to therein as a "wireless system" for supplying power to a plurality of multiple-turn pickup coils disposed in the base of seats throughout an aircraft cabin. Perhaps this technology would more accurately be described as a "connectorless" power supply system, because power is inductively coupled from a power supply loop that is disposed in the base of seats throughout an aircraft cabin to the pickup coils without the use of a direct electrical connection. The power is used to operate the passenger entertainment and service systems installed in the seats. This wireless system permits seats to be moved about in different arrangements as required by individual airline carriers, without concern for providing different length interconnecting wiring harnesses. Not disclosed in the patent are details concerning the regulation of voltage at each of the distributed loads that are inductively coupled to the supply loop.
The wireless power distribution system described in the above patent has been further developed, and now includes a precisely controlled constant current source driving a series resonant supply loop. Since the mutual inductance of the pickup coils appears in series in the supply loop, the constant current source can only maintain a constant voltage at the output of the pickup coil so long as the mutual inductance and load remain constant. However, the mutual inductance is inversely proportional to the distance between the supply loop and the pickup coils, and that distance may vary significantly. In addition, the electrical load imposed on each pickup coil by the entertainment and passenger service systems is likely to vary over a relatively wide range. Due to the existence of these variable parameters, a regulator must be provided for each pickup coil to maintain a constant voltage across its load.
Conventional regulators such as series pass and shunt regulators may produce unacceptable electromagnetic interference (EMI) and possible disruption of the constant current source. In addition, conventional regulators tend to be inefficient, because they dissipate excessive amounts of power, and they typically involve a high part count and an unacceptable cost factor.
In consideration of the above-described problems, it is an object of the present invention to provide a low cost regulator for each load of a connectorless power distribution system. Other objects and advantages of the present invention will be apparent from the attached drawings and the Description of the Preferred Embodiment that follows.